The frequency with which you should back up your files depends mostly on what it is you do.
Backups for Business
If you are a computer professional, you may want to back up your data several times daily, while a casual computer user may only need to create a backup once a week or so. The unfortunate reality is that the vast majority of causal users don’t back up their data at all, leading to huge data losses in the event of a disaster.
A large company will probably have a designated person to create data backups at least once a day, and they will store those backups in more than one place. There may be digital copies stored offsite through the internet, and hard copies stored onsite in a secure location. The secure location, of course, would need to be fire and water proof, as well as being accessible without too much palaver. Assigning one individual to the task allows it to become a regular duty, ensuring that it is done on time all the time. Remember to assign a backup person to the task as well, as your first choice will not be there all the time due to vacation time, illness, or other time off.
How Important is your Schedule ?
Whatever backup schedule you choose, it is vital that you stick to that schedule, since missing a day or two, or even a week, could cause huge problems in the event of a computer crash, or damage to the onsite computers, you will be faced with the loss of all the unsaved data. For a large company with high business volume, this can prove catastrophic.
If you use an online system to create backups of your data, the program can be set to follow whatever schedule you choose. It can also identify which files have been altered since the last backup was created, and automatically save all of those files as well.